MZ motorcycle ts 150 rev counter problem

[jaye b]

Hello to all that read this. I have an issue with my ts 150 rev counter. When the engine has warmed up the rev counter stops working and a rattling noise comes from the clutch housing. The worm drive and other parts behind the clutch have been replaced but the problem persists. Can any one shed light on the issue. Apart from that the bike goes well and starts on the second kick.
Jaye B